Palladium-catalyzed arylation of N,N-dialkylhydrazines and the subsequent conversion to anilines
摘要:
Palladium-catalyzed aminations of different ArBr with N,N-dialkylhydrazines are described. The reaction proceeded in moderate to excellent yield (up to 90%) with good functional groups compatibilities as cyano, ester, ketone and Boc-amine groups are all well tolerated. Several hydrazines were proved to be good coupling partners and this process provided a general method for the isosteric replacement of benzyl amines with arylhydrazines. Moreover, a method for the N-N bond cleavage of arylhydrazines was discovered, and this two-step sequence could be employed as an alternative synthesis of aniline derivatives. (c) 2007 Elsevier Ltd. All rights reserved.
Synthesis of <i>N,N</i>-Dialkyl-<i>N</i><i>‘</i>-arylhydrazines via Palladium-Catalyzed N-Arylation by Using <i>N,N</i>-Dialkylhydrazines/2LiCl Adducts
[GRAPHICS]The reaction of N,N-dialkylhydrazine/2LiCl adducts with aryl bromides in the presence of Pd-2(dba)(3) as the palladium source, Xantphos or X-phos as the ligands, toluene as the solvent, and NaOBu-t as the base provides an efficient route to N,N-dialkyl-N,-arylhydrazines. Best results were obtained by using N,N-dialkylhydrazine/2LiCl adducts prepared in situ, omitting their isolation.